1. Field of the Invention
The present invention relates to an inductive detection encoder and a digital micrometer which measure a position and a size of an object using magnetic flux coupling between wiring lines.
2. Description of the Related Art
An inductive detection encoder, which allows an inductive current to flow in a magnetic flux coupling coil by a transmitting coil and receives the inductive current by a receiving coil to measure a relative position of the magnetic flux coupling coil and the receiving coil, is known (see Japanese Published Patent Application No. 2010-210472). The inductive detection encoder has excellent resistance to the environment and is used for various purposes such as a linear encoder or a rotary encoder.
The inductive detection encoder measures the position using an inductive current. For example, in the case of a rotary encoder, a transmitting coil is formed in a circular shape and a magnetic flux coupling coil is formed to be a gear shape or a loop shape so as to be arranged in a circumferential direction with a predetermined interval. An alternating current flows into the transmitting coil to generate a magnetic field, which causes the inductive current to flow in the magnetic flux coupling coil. A periodic magnetic field pattern in the measurement direction generated by the inductive current is detected by the receiving coil. Therefore, if the transmitting coil is ideally circular and the receiving coil has a uniform shape in a circumferential direction, it is expected to obtain an ideal signal in the receiving coil.
However, a leading wiring unit needs to be provided in the transmitting coil so as to supply a power and a leading wiring unit needs to be provided in the receiving coil so as to draw a signal. Accordingly, the disturbance in the magnetic field generated in the leading wiring units affects a reception signal generated by the receiving coil, which causes a measurement error.